San Helios was in the Scorpion Nebula, on the other side of the universe from Earth. It had three suns, two blue and one red. The Tenth Doctor believed that they had the ability to enhance psychic powers, increasing Carmen's precognition. It appeared to have gravity and atmosphere roughly equivalent to Earth. San Helios originally had a varied topography, with oceans, forests and deserts, but after the attack by the Swarm, the whole planet was covered in a sand-like substance. (TV: Planet of the Dead)